Chelsea have been encouraged by the news that there is a fee which could trigger a deal, although sources have said that it is higher than the €26.9m reported earlier this week.

Stamford Bridge owner Roman Abramovich will not be put off by a €30m-plus clause if he is convinced that Fellaini is the man who can add greater steel to Chelsea’s midfield and dovetail with their battery of nimble, attacking midfielders.

Although the imposing Belgian has been used almost exclusively behind the main striker at Everton this season, he has said publicly that he regards his best position to be defensive midfield.

Arsene Wenger is a long-time admirer of Fellaini and tried to sign him before buying his former colleague Mikel Arteta from Everton in the summer of 2011 but Arsenal will not get involved in an auction with Chelsea.

There is also interest in Fellaini from the continent yet Chelsea are the frontrunners to acquire a player who has been in outstanding form this season, scoring nine goals to help lead David Moyes’ side to fifth in the Premier League.

Fellaini revealed during the September international break that this could be his final season at Goodison Park, claiming: “In January or at the end of the season I will turn to another club or championship."

Sources have told Goal.com that the west Londoners closely monitored Fellaini during the summer window, even up until the final week of August, but were told that the 25-year-old would remain on Merseyside for at least another window.

The versatile midfielder signed a new five-year deal in November 2011, which was when the release clause was inserted into his contract.

Fellaini, who became Everton’s record signing when he moved from Standard Liege for an initial €17m (a club-record £15m at the exchange rates of the time) in 2008, is attracted by the possibility of moving to a club who compete regularly in the Champions League.

Chelsea are in the market for a central midfielder after loaning Michael Essien to Real Madrid in the summer, selling Raul Meireles to Fenerbahce and losing Oriol Romeu to a knee injury that will keep the Spaniard out for the rest of the season.

Lampard will also leave Stamford Bridge at the end of the season after being told that he will not get another contract from the club he joined in 2001.

Manager Rafael Benitez has been forced to use centre-back David Luiz in midfield over the past month, albeit with some success, while the club’s regular midfield anchorman John Obi Mikel has left for Africa Cup of Nations duty with Nigeria.